I recently picked it a E30 325i all original, no rust, and no accidents (from California) for a steal. Anyway, I know this has probably been beaten to death and I've searched all over with no real answer that I can find. So, my question is this... it came with a complete M52 swap with all accessories. I'm looking to turbo it. It's currently on an engine stand as I'm tearing it down to rebuild. I want to build it it to be reliable while putting down a lot of power like 600ish. Can I rebuild my M52 head to S52 spec or do i need a complete new head due to valve springs? Can i use a S52 rotating assembly (aside from pistons) and achieve the same result? Should i bore the block or will cylinders be too thin? What size turbo should i go with? I plan on using a m50 intake manifold and probably 8.5:1 pistons... as of now. Any help would be appreciated. Thanks!